1. Technical Field
The present invention relates to controlling behaviors of a variety of electro-optical elements such as light emitting elements represented by organic light emitting diodes (hereinafter, referred to as “OLED”).
2. Related Art
As display units or exposing units of a variety of electronic apparatuses, electro-optical devices in which a plurality of electro-optical elements are arranged have been suggested. The gray scales (for example, brightness) of the electro-optical elements are controlled in accordance with data signals supplied to data lines corresponding to the electro-optical elements. A configuration employing a plurality of semiconductor chips or supplying the data signals to a plurality of data lines is also known. In the respective semiconductor chips, data signals corresponding to the gray scales are generated with reference to current (hereinafter, referred to as “reference current”) generated from the semiconductor chips.
However, difference in characteristics (for example, threshold voltage) due to manufacturing processes can occur between the semiconductor chips. Accordingly, even when the same gray scale is specified for the electro-optical elements, there is caused a problem that the gray scales of the electro-optical elements are different because the reference current serving as a basis of the data signals is different for the semiconductor chips. In order to solve the problem, a configuration of supplying all the semiconductor chips in common with the reference current generated from one reference current generating circuit is disclosed in JP-A-2000-293245 (see Paragraph No. 0008 and FIG. 1). In addition, a configuration of supplying a signal corresponding to the reference current of each semiconductor chip to a semiconductor chip adjacent thereto for use in generating the data signals is disclosed in JP-A-2005-49632 (see Paragraph No. 0042 and FIG. 2).
However, in the configuration disclosed in JP-A-2000-293245, since wires for electrically connecting the reference current generating circuit to the semiconductor chips are elongated, there is a problem that the reference current supplied to the semiconductor chips from the reference current generating circuit can be easily varied due to a variety of factors such as noise from the peripheral circuits. On the other hand, in the configuration disclosed in JP-A-2005-49632, the reference current is varied accumulatively every time of supplying the reference current to the semiconductor chips due to a variety of factors such as variation in characteristics of the semiconductor chips or superposition of noises in the wires. Accordingly, there is a problem that the reference current supplied to a downstream semiconductor chip in the flow direction of the reference current is further deviated from a predetermined current value.